Researchers are studying the connections between sleep apnea and Alzheimer's
Obstructive sleep apnea can increase the risk of developing Alzheimer's disease in older people. Biomarkers for amyloid beta increase over time in older adults with sleep apnea. The more pronounced the sleep apnea, the more the values of these biomarkers increase. So if people suffer from more apneas per hour, this leads to a greater accumulation of hirnamyloid.
In their current study, scientists from the New York University School of Medicine found that people with sleep apnea are at increased risk of developing Alzheimer's. The doctors published the results of their study in the American Journal of Respiratory and Critical Care Medicine.
Causality for links between Alzheimer's and sleep apnea has so far been difficult to verify
Alzheimer's is a so-called neurodegenerative disease that affects around five million older Americans alone. Sleep apnea is even more common and affects 30 to 80 percent of the elderly, depending on the definition of sleep apnea, the authors say. Various studies have already concluded that sleep disorders contribute to amyloid deposits and can accelerate cognitive decline in people at risk of Alzheimer's, explains Dr. Ricardo S. Osorio from New York University School of Medicine. So far, however, it has been difficult to check the causality for this compound because Alzheimer's and sleep apnea share certain common risk factors and often coexist, the expert adds.
Doctors examine amyloid deposits in people with sleep apnea
The purpose of the current study was to examine the associations between the severity of sleep apnea and changes in biomarkers for Alzheimer's. It was particularly interesting for the researchers whether the so-called amyloid deposits increase over time in healthy older participants with sleep apnea.
Researchers examine 208 subjects
For their study, the experts examined 208 participants between the ages of 55 and 90 with normal cognition, which was measured by standardized tests and clinical assessments. The participants were not referred from a sleep center, did not use CPAP ventilation, were not depressed, or suffered from medical conditions that impair brain function, the scientists explain.
104 subjects took part in the two-year longitudinal study
The investigation found that more than half of the participants suffered from sleep apnea, including 36.5 percent with mild sleep apnea and 16.8 percent with moderate to severe sleep apnea, the researchers say. 104 of the subjects then took part in a two-year longitudinal study. The results of this study showed an increase in amyloid deposits in the brain.
Changes take place in the preclinical stages of Alzheimer's
Surprisingly, this study was unable to determine that the severity of sleep apnea can predict cognitive deterioration in healthy older adults, reports author Dr. Andrew Varga from the Icahn School of Medicine at Mount Sinai in New York. This finding suggests that these changes occurred in the preclinical stages of Alzheimer's.
Results may be due to limitations in the investigation
The relationship between amyloid exposure and cognition is likely not linear and depends on additional factors, the expert explains. This study finding could also be due to the relatively short duration of the study, highly-educated participants and the use of tests that do not detect subtle or sleep-dependent changes in cognitive abilities.
Using better screening tools would be tremendous
The results from this and other studies suggesting sleep apnea, cognitive decline, and Alzheimer's are related. The well-known effects of sleep apnea such as drowsiness, cardiovascular and metabolic dysfunction may be the cause of increasing brain impairment in old age, explains Dr. Osorio. If this were the case, the potential benefit of developing better screening tools to diagnose sleep apnea in the elderly would be enormous, the expert added. (as)